Learn CSS Positioning in Ten Steps: position static relative absolute float http://www.barelyfitz.com/screencast/html-training/css/positioning/
Get down! How to keep footers at the bottom of the page http://matthewjamestaylor.com/blog/keeping-footers-at-the-bottom-of-the-page
The Perfect 3 Column Liquid Layout: No CSS hacks. SEO friendly. iPhone compatible. http://matthewjamestaylor.com/blog/perfect-3-column.htm
Three column CSS layout: 100% height with footer | Strictly CSS http://www.strictlycss.com/examples/three-column-layout-6.asp